Sen Joseph Biden (D) - who chairs the Foreign Relations Committee - said on Tuesday that the surge had failed to promote reconciliation between Sunnis and Shia, and was at best "a stopgap that will not prevent chaos".

House of Representatives Speaker Nancy Pelosi (D) said: "It sounds to me as if Gen Petraeus is presenting a plan for at least a 10-year, high-level US presence in Iraq."

Gen Petraeus said that violence in Iraq had declined significantly since February, but stressed that a premature troop reduction would have "devastating consequences".

A record 168,000 US troops are now in Iraq after 30,000 arrived in the surge between February and June.